Project Abstract Acquired apraxia of speech (AOS) is a neurologic speech disorder that is characterized by slowed rate of speech, difficulties in sound production, and disrupted prosody. There are limited data concerning its prevalence, but Duffy (2005) reported that AOS was the primary communication disorder in 7.6% of 6101cases of neurologic motor speech disorders. As a secondary diagnosis (e.g., accompanying aphasia) AOS occurs even more frequently. The AOS treatment evidence base is meager in terms of both quantity and quality of AOS treatment investigations. However, sufficient data exist to support the statement that behavioral treatments for AOS may be expected to result in improvements in speech production even when AOS is chronic (Wambaugh et al., 2006). The purpose of the proposed research is to examine the effects of a treatment for AOS with speakers with chronic, moderate-severe to mild-moderate AOS. The impact of the motor learning variables of random practice and blocked practice will be investigated with application of Sound Production Treatment (SPT). The planned investigation is designed to explicate the acquisition, maintenance and generalization effects of SPT administered using the two types of practice. A combination of group and single-subject experimental designs will be utilized. Twenty-four participants with AOS will be assigned to one of two treatment groups (12 per group). One group will receive SPT-Blocked followed by SPT- Random. The other group will receive the treatments in the reverse order (SPT-Random followed by SPT-Blocked). Each participant will receive treatment administered in the context of a single-subject, multiple baseline design across behaviors. The primary dependent variable will be articulation of speech sounds. A baseline phase will be conducted with each participant, followed by application of either SPT-Blocked or SPT-Random. A two week period of no treatment will follow the first phase of treatment. During this period, extended baselining of the untrained behaviors will occur to ensure stability of responding prior to the second phase of treatment. At the end of the two week period, probing will occur to measure short term maintenance of trained behaviors. After the two week period, the second treatment will be applied to the remaining set of behaviors. Follow-up testing of all behaviors will occur at 2, 6, and 10 weeks after the cessation of all treatment. Performance across groups will be compared in terms of rate of acquisition of trained behaviors (i.e., articulation of targeted speech sounds) and effect sizes. Performance within groups and within individuals will also be evaluated. In addition, unfamiliar listeners (certified speech/language pathologists) will perform ratings of speech naturalness and intelligibility using pre- and post-treatment speech samples.